1. Field of the Invention
This application relates generally to a liquid crystal display (LCD) in a mobile communication device. More particularly, the invention provides a system and method for achieving optimal display contrast in mobile communication devices, such as Personal Digital Assistants, cellular telephones, and wireless two-way e-mail communication devices (collectively referred to herein as “mobile devices”).
2. Description of the Related Art
Mobile devices typically include a liquid crystal display (LCD) to display information to the mobile device user. Known mobile devices enable the mobile device user to control the contrast of the LCD with an external user interface, such as a thumb wheel. Contrast is the difference in luminance between an on and an off pixel on the LCD. The contrast range on a typical LCD is generally unduly broad, leaving only a small range over which a mobile device user will typically set the preferred contrast. For instance, if the user of a typical mobile device can control the contrast of the mobile device's LCD using a thumb wheel, then the extremely high position of the thumb wheel will generally result in all of the pixels being dark and the extremely low position of the thumb wheel will generally result in all of the pixels being light. At either the high or low contrast setting, the user will typically not be able to ascertain the difference between on and off pixels. It is typically only within a range of settings between the extremely low and high positions of the thumb wheel that a desired contrast setting may be achieved.
In addition, the contrast in an LCD often varies significantly from one LCD manufacturer to another, and may even vary between two LCDs from the same manufacturer. This deviation in LCD contrast makes it difficult for a mobile device manufacturer to calibrate the LCD in each mobile device to an optimal contrast setting before delivery to the user. For instance, the optimal LCD contrast setting on one mobile device may be at a point below the center of its contrast range, while the optimal contrast setting on another mobile device may be at a point above the center of its contrast range. As a result, mobile device manufacturers must often special order LCDs to match particular operating voltage specifications, increasing the cost of the display and thus the mobile device.